1. Field of the Invention
This invention relates generally to the electronic control art, and more particularly, to a novel electronic control system for controlling a sequence of operations on products moving on an indexing conveyor, such as a sequence of operations carried out on containers by a packaging machine.
2. Description of the Prior Art
It is known in the packaging art to provide pneumatic or air control systems for controlling operations carried out at various work stations on cartons in a packaging machine, such as filling operations, sealing operations and so forth. The aforedescribed prior art logic systems are entirely pneumatic systems employing air control valves, and mechanical detectors or levers which control the operation of the apparatuses at the work stations, as for example, the filler apparatus at the filling stations, and the carton sealing apparatus at the sealing station. The mechanical detectors or levers operate the air control valves which in turn operate the filler cylinders of the filler apparatus. In an air logic system, with a four station filler apparatus, there are four mechanical detectors required to operate the four cylinders in such an apparatus. A problem resulting from the use of such mechanical detectors is that they must be located in the immediate filler discharge area, whereby they are subject to spillage and other contaminants which injuriously affect the operation of such mechanical detectors.
A further disadvantage of the prior art logic control systems described above is that each filler cylinder is employed to dispense product into every carton, and under some circumstances, such as smaller capacity cartons, some of the filler cylinders are not operated which results in stagnation of product in the filler valves due to non-use.
Another disadvantage of the prior art filler control apparatus is that the non-use of some filler cylinders as described in the previous paragraph results in non-uniform wear of the filler parts from cylinder to cylinder which results in degradation of calibration uniformity.
The prior art air logic filler control systems also produces an unbalanced mechanical loading on the filler drive mechanism when some of the filler valves are not used for a filling operation. The last mentioned imbalance of mechanical loading causes a non-uniform wear on all of the moving parts of the filler drive mechanism.
Another disadvantage of the aforedescribed prior art air logic filler control systems is that the mechanical detectors or levers employed in such systems must make a large contact area and exert a somewhat large force on each of the cartons as they are moved to a filler station which actions result in damage in certain instances to the cartons.
Still another disadvantage of the prior art filler control systems is that the clean-in-place (C.I.P.) system for cleaning the filler apparatus requires an external mechanical timing device and other associated external equipment which is separate from the air logic control apparatus for the filler valves.